Frog Jump

A frog starts on stone 0 and wants to reach the last stone. From stone i it can jump to i + 1 or i + 2. A jump from i to j costs |heights[i] − heights[j]|. Return the smallest total cost.

Examples

Example 1

Input:  heights = [10, 20, 30, 10]
Output: 20

0 → 1 (cost 10) → 3 (cost 10) = 20. Going 0 → 2 → 3 would cost 20 + 20 = 40.